CVE-2026-16044 Insufficient validation of guest board admin privileges on archive import
A board member can escalate a guest user to Board Admin by importing a crafted archive file due to insufficient privilege validation.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-16044?
CVE-2026-16044 is a low-severity vulnerability in Mattermost Mattermost Server, published on 17 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21 fail to prevent guest users from receiving Board Admin privileges during board archive import which allows a board member to escalate a guest user to Board Admin via importing a crafted .boardarchive file. Mattermost Advisory ID: MMSA-2026-00672
Weakness: CWE-863
Which versions are affected by CVE-2026-16044?
It affects 1 product.
Products include Mattermost Mattermost Server.
How do I fix CVE-2026-16044?
Apply the vendor's patch.
Is CVE-2026-16044 being exploited?
There is no known exploitation of CVE-2026-16044 in the wild and no public exploit code.
Other vulnerabilities in Mattermost Mattermost Server
- CVE-2025-12419 Account takeover on OAuth/OpenID-enabled servers
- CVE-2025-12421 Account Takeover via Code Exchange Endpoint
- CVE-2025-4981 Path Traversal Leading to RCE by Any Authenticated Mattermost User
- CVE-2025-20051 Arbitrary file read via block duplication in Mattermost Boards
- CVE-2025-25279 Arbitrary file read in Mattermost Boards via import & export board archive
Sources
Also known as GHSA-496c-r634-6cgj, MINI-4585-p8cx-8cfh, MINI-95f2-f88g-4h6v.